The present invention relates to a device for operating a controlled member on a rotary-wing aircraft, particularly a helicopter.
In the case of a helicopter, said controlled member may be the main lift and forward propulsion rotor or the countertorque tail rotor.
More specifically, the present invention applies to a rotary-wing aircraft equipped with an automatic control system, that is to say a system that assists with stabilizing or increasing the stability of the aircraft.
As is known, the device for operating the main rotor or the tail rotor of a helicopter comprises:
at least one control, for example a stick or rudder bar, intended to be subject to the action of a pilot of the aircraft and capable of moving a linkage;
means, generally a servocontrol, connected to said linkage for operating the controlled member as a function of the movement of said linkage;
a ram incorporated into the linkage and capable of influencing the movement of said linkage as a function of control commands received and which represent the automatic control;
a trim means, usually known as a xe2x80x9ctrim ramxe2x80x9d and which is capable of acting via a flexible link (spring box for example) on the control and on the linkage as a function of control commands received and which represent the automatic control; and
a computer determining said control commands which are transmitted to said ram and to said trim means.
Said control commands relating to the automatic control are therefore combined with those generated by the action of the pilot on the control.
This automatic control is essentially intended to lessen the extreme effects of the operation of the control, particularly with a view to stabilizing the aircraft.
Although the aforementioned device is very safe and reliable because it is essentially a mechanical system (linkage), the control achieved using such a device displays drawbacks and, in particular, is less comfortable, particularly by comparison with fly-by-wire controls, and finds it increasingly difficult to meet all the requirements that have to be met by a present-day rotary-wing aircraft, the missions of which require extremely high performance.
It is known that fly-by-wire controls give better performance control, particularly as far as flight comfort is concerned.
As is known, such fly-by-wire controls comprise a computer which, using so-called evolved laws, determines control objectives as a function of information relating to the operation of the control and which achieves these objectives in such a way as to obtain the aforementioned high-performance control.
However, such fly-by-wire controls have drawbacks, particularly:
high cost, particularly compared with the cost of a conventional automatic-control device like the aforementioned; and
the need to provide means capable of compensating for any failure, even partial failure, of these fly-by-wire controls.
To achieve this, there is generally redundancy between the various elements of said fly-by-wire controls, and this is of course complicated and expensive.
The object of the present invention is to overcome these drawbacks. This invention relates to a device for operating a controlled member on a rotary-wing aircraft, particularly a helicopter, which, while at the same time being lower in cost and more dependable, provides particularly high-performance control.
To this end, according to the invention, said device which comprises:
at least one control intended to be subject to the action of a pilot of the rotary-wing aircraft and capable of moving a linkage;
means, generally a servocontrol, connected to said linkage for operating said controlled member as a function of the movement of said linkage;
a ram incorporated into the linkage and capable of influencing the movement of said linkage as a function of control commands received;
a trim means (xe2x80x9ctrim ramxe2x80x9d) capable of acting on the control and on the linkage as a function of control commands received; and
a computer determining said control commands which are transmitted to said ram and to said trim means,
is noteworthy in that it additionally comprises at least one sensor which is capable of measuring the values of a parameter that represents an action exerted by a pilot of the rotary-wing aircraft on an auxiliary control, and in that said computer uses the values measured by said sensor to determine said control commands with a view to creating control objectives.
Thus, by virtue of the invention, said computer can determine control commands from known evolved laws of the type used in fly-by-wire controls, so that said device, although being of the conventional type with automatic control, allows the rotary-wing aircraft to be controlled using objectives.
As a result, the device in accordance with the invention:
allows high-performance control of the type achieved with fly-by-wire control;
while at the same time displaying:
high dependability, owing to the fact that it is essentially a mechanically-based system and can continue to operate when its electrical part (essentially the computer) breaks down; and
a low cost, because it is based on a conventional mechanical device and requires no redundancy between its constituent elements.
In the context of the present invention, said computer takes into account, when calculating said control commands, information from the pilot, but which differs from the actual position of the control. As a preference, according to the invention, the parameter measured by said sensor and taken into account by said computer is:
either the force applied by the pilot to the auxiliary control;
or the relative movement of said auxiliary control with respect to the position of the trim means.
The present invention is particularly applicable to an aircraft in which the trim means is activated, in the usual way, when said control is not being operated by the pilot.
In this case, said trim means is advantageously also activated when the control is being operated by the pilot.
In the context of the present invention, the control and the auxiliary control may be produced in different ways.
In a first, simplified, embodiment, they form one and the same control, whereas in a second embodiment, said control and said auxiliary control are separate and are set out on the rotary-wing aircraft in such a way as to be accessible and operable by one and the same pilot of said aircraft.
Furthermore, in a third embodiment applied to a rotary-wing aircraft flown by two pilots, advantageously said control is subject to the action of one of said pilots and said auxiliary control is subject to the action of the other pilot.
In the aforementioned second and third embodiments, said control is preferably a conventional control of the cyclic stick or rudder bar type and said auxiliary control is of the mini-stick type.
Furthermore, in a fourth, improved, embodiment, said control and said auxiliary control are adapted to one another so as to form a single assembly, while at the same time being able to be operated separately.